The present invention relates to a self-blocking forceps for raising slabs, such as plates, metallic or concrete slabs, ingots and similar products.
In all industrial fields and in particular in the mechanical field for working metals, it is necessary to use tools, defined with the generic term forceps, capable of moving semi-worked products as sheets and capable of transporting the products from one department to another for working the products. In the building sector such sheets or slabs are made of concrete.
These types of forceps are essentially constituted by two jaws made of hard steel, which are connected one to the other in such a manner that they may be closed or opened and having their heads shaped in different manner depending upon the use for which they are intended and which are of the type called xe2x80x9cself-blockingxe2x80x9d, that is they guarantee automatic locking when they come in contact with the product being moved.
In the present state of the art there are known many types of forceps as described in U.S. Pat. Nos. 3,843,186; 4,273,373, 4,497,201; East German Publication 276,852; G.B. 1385772, E.P. 0233386.
An object of the present invention is to provide a self-blocking forceps which is constructively simpler than similarly known devices and at a lower cost than the forceps at present in commerce.
This object is achieved by means of a self-blocking forceps composed by three items: a fixed body for the forceps, a cam and a movable carriage which carries the cam.
In more detail, the fixed body forceps which is provided with an opening for the insertion of the hook used for raising the material, has a fixed jaw which comes in contact, in an antagonistic manner with the pushing force which is generated by the counterposed cam. In this manner the closure on the material referred to hereinbelow by the generic term plate is achieved.
A further novel feature of this invention provides that the cam is mounted on the lower end of the movable carriage in an idle way and with a suitable profile so that after the cam has been manually approached to the surface of the slab, due to the manual displacement of the carriage the cam performs a very small angular rotation, which is sufficient to generate the necessary gripping force for the anchoring of the slab.
The cam has a shaped profile for the purpose of guaranteeing the anchoring of slabs of different thickness.
Still constructively this invention provides further novelty, that the movable carriage has the upper end, opposite to the end supplied with the cam and which slides within a slot formed on the fixed body, resting against a block which is integral with the fixed body, the entire device being shaped in a manner that the carriage becomes self-blocking under the weight of the material due to the pushing action of the cam when the latter is in a position of anchoring the slab.